The data center is at the foundation of modern software technology, serving a critical role in expanding capabilities for enterprises. A data center design called the network-based spine-and-leaf architecture was developed to overcome several limitations of older network architectures. This architecture has been proven to deliver high-bandwidth, low-latency, and non-blocking server-to-server connectivity. In this two-tier Clos architecture, every lower-tier switch (leaf layer) is connected to each of the top-tier switches (spine layer) in a full-mesh topology. The leaf layer consists of access switches that connect to devices such as servers. The spine layer is the backbone of the network and is responsible for interconnecting all leaf switches. Every leaf switch connects to every spine switch in the fabric. The path is randomly chosen so that the traffic load is evenly distributed among the top-tier switches. If one of the top tier switches were to fail, it would only slightly degrade performance throughout the data center.
If oversubscription of a link occurs (that is, if more traffic is generated than can be aggregated on the active link at one time), the process for expanding capacity is straightforward. An additional spine switch can be added, and uplinks can be extended to every leaf switch, resulting in the addition of interlayer bandwidth and reduction of the oversubscription. If device port capacity becomes a concern, a new leaf switch can be added by connecting it to every spine switch and adding the network configuration to the switch. The ease of expansion optimizes the IT department's process of scaling the network. If no oversubscription occurs between the lower-tier switches and their uplinks, then a non-blocking architecture can be achieved.
With a spine-and-leaf architecture, no matter which leaf switch a server is connected, its traffic always has to cross the same number of devices to get to another server (unless the other server is located on the same leaf). This approach keeps latency at a predictable level because a payload only has to hop to a spine switch and another leaf switch to reach its destination.